The town of Greensburg, Indiana, is known as the “Tree City” for the over a dozen trees that have been growing out of the roof of the Decatur County Courthouse ever since 1870. They are believed to have sprouted from seeds in bird droppings.

In the year 1870, the citizens of Greensburg began to notice what looked like a small sprig growing on the northwest corner of the courthouse tower. No one paid much attention to it at first, but as the shrub grew into a young tree, it became the talk of the town. A few years later, five new sprouts were spotted on the tower roof, threatening to form a small grove atop the 110-foot-tall tower. Authorities were worried the tree roots might cause irreparable damage to the roof, so in 1888 a steeplejack was hired to cut down the smaller trees, leaving just one, which in time grew to about fifteen feet with a diameter of almost five inches at its base. It continued to brave the storms for many years, until it finally died, and was removed to a place in the Decatur County Historical Society Museum. But that was not the end of the now famous courthouse tower tree. In the meantime, another tree appeared on the southeast corner of the tower, and grew to a considerable height in just a few years time.

According to some reports, courthouse tower grows new trees constantly and steeplejacks have to climb up to remove them and trim the main tree. When it gets too old or diseased they take it down and allow another one to take its place. The species to which these trees belong to has been a mystery for a long time. Some believed they were linden, others that they were of the silver poplar variety, but a scientific classification by the Smithsonian Institute established they were actually of the large tooth aspen variety. That solved the mystery for a while, until 2007, when several foresters from the Purdue University the current tree as a Mulberry tree.

But the debate around the species of the Decatur County Courthouse tower tree pales in comparison to that regarding its source of nourishment. How does a tree survive atop a wooden roof? Some believe the believe that dust from the interior as well as dust and moisture from the outside provide the necessary sustenance, but that remains only a theory. Others jokingly claim the tree is fed by springs in the tower clock.